Studies will be performed in the dog in which arachidonic acid an/or prostaglandins will be infused into the renal artery. Various renal functions and renal blood flow (electromagnetic flow probe) will be measured under a variety of conditions to determine whether the renal effects of prostaglandins are mainly tubular or vascular. The effects of diets rich in arachidonic acid (prostaglandin precursor) on the blood pressure of spontaneously hypertensive rats will be studied. Studies on the sensitivity of the renal vascular bed of neonatal puppies to vasopressor agents will be continued. The role this sensitivity plays on salt handling will be determined.